1. Field of the Invention
The present invention relates generally to a semiconductor package and a package stack using the same and, more particularly, to a semiconductor package having a heat spreader and a package stack using the same.
2. Description of the Related Art
The electronics industry continues to seek products that are lighter, faster, smaller, multi-functional, more reliable and more cost-effective. One of the important technologies making these objectives possible is semiconductor packaging technology by which a chip scale package (CSP) was recently realized. CSP technology provides a small sized package having the size level of a semiconductor chip.
A semiconductor package having a large capacity as well as small size is also required. However, to improve the capacity of a semiconductor package a technique to put a large number of cells into a semiconductor chip of restricted space is required which needs a higher level of technologies, such as minute line pitch and enough developing time. Therefore, currently, research is directed toward realizing a high degree of integration within semiconductor chips or semiconductor packages already developed. For example, package stacks are produced by stacking a plurality of semiconductor chips or semiconductor packages in three dimensions.
Package stacks may be manufactured by stacking packages that have already passed the necessary tests for their functions. Therefore, the yields and reliability of these package stacks may be higher than those stacked chip packages manufactured by stacking a plurality of chips without being tested. However, the package stacks may be thicker as compared with stacked chip packages because of the thickness of each individual package stack.
A semiconductor package suitable for high speed and performance generates a large quantity of heat during the operation, which results in degeneration of performance. Therefore, for the purpose of improving heat dissipation capability, a heat spreader attached to the semiconductor package has been used as in U.S. Pat. No. 6,410,988, No. 6,486,554 and Korean Patent Publication No. 2000-28359.
However, since the heat spreaders in the prior art have a structure where a thermal conductive pad is simply attached on the rear side of a molding body or a semiconductor chip, the prior art merely improved heat dissipation while not improving electrical performance. This kind of structure in the prior art can even cause electromagnetic interference (EMI) problems.
To prevent the degeneration of electric performance and to further improve electrical performance, Japanese Patent Publication No. 2000-114413, Korean Patent Publication No. 2002-76837 and No. 2003-41653 suggested a technique of contacting a heat spreader with a ground terminal of the semiconductor package.
However, the semiconductor package having grounded a heat spreader is not suitable for a package stack within the structure disclosed in the prior art. Those structures need additional means for electric connection between a lower package and an upper package because the upper package is placed on the heat spreader of the lower package, which results in increasing the thickness or width of the package stack.